Automatic volume control receiver



May 23, 1939.

E. KLOTZ Filed March 10, 1937 DELAYED A VC I. F. AMPL- l I X i J 4 2wvosmrsa AI/C J INVENTOR z ERNST KLOTZ ATTORNEY M (AF-NETWORK) m 40 1,tential arising across resistance W so that across tion of volumecontrol means oifers the advan- Patented May 23, 1939 PATENT OFFICEAUTOMATIC VOLUME CONTROL RECEIVER 'Ernst Klotz, Berlin, Germany,assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b.11., Berlin, Germany, a corporation of Germany Application March 10,1937, Serial No. 130,082 In Germany March 12, 1936 1 Claim. (01. 250*20)The use of means insuring a lag in the opera- 3 1 tage that the maximumamplification of the re- ;ceiver is not diminished. However, it involvesthe drawback that the tuning indicator is ren-,

dered operativeonly when the regulation, or

compensation, of the fading, i. e., automatic volume control, becomesoperative or is initiated.

In other words, when feeble stations are received the tuning indicator,as a matter of fact, would not be necessary at all in that case seeingthat {adjustment by ear is possible.

the volume control means is inoperative, so that However, it is highlydesirable for the user, or operator, of the set to be in a position,also in the reception of *feeble stations, to tell from the tuningindicator 1 whether a desired station is being received or not, and tobe enabled to adjust the tuning by reading the indicator to the propervalue. In case silent tuning is desired the tuning indicator is jabsolutely necessary. In other words, there exists Q a certainconflicting situation which is to be eliminated by the ways and meansdisclosed in the present invention. l 25;

is included in the plate circuit of a tube which is According to theinvention, the tuning indicator {not subject todelayed gain regulation,and whose gain isless changed by the regulation than that g j l s ot theother tubes in which a lag of regulation is occasioned. i

The invention shall be explained in more dej-fltail by reference to thedrawing wherein there is shown a superheterodyne receiver. In the mixer,or combined oscillator-first detector, tube M, the

l lation circuit E is changed into the intermediate incoming, or signal,oscillation fed to the oscilfrequency, and by way-of the band-passfilters 2F and the I. F. amplifier tubeZ the I. F. energy [is fed to thesecond detector stage G. The left diodeof tube G isnegatively biased bythe podiode load resistanceWr, with small incoming amplitudes, noregulation will as yet be initiated.

fI'he right-hand diode sets up across the resistance W2 a regulatorpotentialeven when the I. F. carrier amplitudes are small, and this gainregulation voltage is impressed upon the I. F. tube Z. The plate circuitof the latter contains means for controlling the first detector gainwith the tuning indicator, which, as will be noticed, is renderedoperative also when feeble stations are coming in. The voltage acrossresistor W1 is used to control the gain of the first detector tube.

The tube which is subject to undelayed regulation should be regulatedbut little in its gain in order that, when signals from feeble stationsare collected by the set, the amplification of the receiver may be butinappreciably reduced. Otherwise, the leg in volume control provided inthe other tubes would be illusory. In the instance here shown anddiscussed, weak regulation of the I. F. tube Z would be required becauseit is located directly ahead of the diode so that, in case a powerfultransmitter is received, distortions due to overload will be avoided, anaction that would not happen if the regulation is unduly great. Weakregulation may be insured either by the use of a tube whosecharacteristic rises slowly, or else by tapping only part of the gainregulation potential.

It would, also, be conceivable to include the tuning indicator in a weakinput tube which is not subject to lag in regulation. However, thisscheme is less favorable for the reason that it is desirable that apowerful regulator action should be brought upon the first tube. Itwould, also, be unfavorable to include the tuning indicator in the platecircuitof the mixer tube for the reason that the plate current of thesame is a function of the amplitude of the oscillator wave which issubject to slight changes inside the wave band.

What is claimed is:

In a superheterodyne receiver of the type including a first detectortube, an intermediate frequency amplifier and an audio network, arectifier coupled to the amplifier and providing direct current voltage,a gain control circuit impressingthe direct voltage on the amplifier toreduce its gain as soon as signals are received, a second rectifiercoupled to the amplifier to provide a second direct current voltage,means for delaying the rectification of the second rectifier,

the second voltage, and a tuning indicator in the amplifier spacecurrent path.

ERNST KLOTZ.

